Question

when taking a 19 question multiple choice test ,where each question has 3 possible answers ,it would be unusual to get or more questions correct by guessing alone consider "unusual " to be more than two standard deviations away from expected.

Answer 1

we have that

You have 1 in 3 probability of guessing the correct answer for a single question

you have 19 opportunities to guess

so

19*(1/3)=19/3=18/3+1/3=6 1/3

therefore

would be unusual to get 7 or more questions correct by guessing alone